Adaptive linear linked piston electric power generator

ABSTRACT

A load adaptive linear electrical generator system is provided for generating DC electrical power. The electrical generation system includes one or more power generation modules which will be selectively turned on or off and additively contribute power depending on the DC power demand. Each power generating module includes a pair of linear electrical generators connected to respective ones of a pair of internal combustion piston based power assemblies. The piston in the internal combustion assembly is connected to a magnet in the linear electrical generator. The piston/magnet assembly oscillates in a simple harmonic motion at a frequency dependent on a power load of the electrical generator. A stroke limiter constrains the piston/magnet assembly motion to preset limits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional application 62/488,990,filed on Apr. 24, 2017, which is herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

The present invention relates to the incorporation of internalcombustion engines coupled to electrical generators. More particularlyto the field of linear piston electrical energy generators, which can beincorporated into hybrid vehicles or operate as a stationary electricalpower generation system.

Linear piston engines in the form of free piston engines have been inexistence for over 75 years. In their simplest form, they consist of anunattached piston shuttling back and forth in a cylinder assembly. Onone end of the cylinder is a return or bounce spring, and on theopposing end of the cylinder is the combustion head with the fuel/airmixture acting as a spring during a compression stroke. Intake andexhaust ports would be located in the cylinder walls creating a“two-stroke” internal combustion engine. Combustion is initiated in thearea where the cylinder head is attached using compression ignition.Starting this form of free piston engine was typically done usingcompressed air. The compressor of the fuel/air mixture at the head wouldact as an “air spring”. When the fuel/air mixture was sufficientlycompressed, the mixture would then become hot enough to ignite themixture sending the piston back down the cylinder. The bottom springreverses the piston direction back to the cylinder head. Once initiatedand running, the endless cycle of piston shuttling becomesself-sustaining. To achieve a sufficient ignition temperature in coldweather, an electrical glow plug might be activated in the pistoncylinder head to assist in heating the air mixture during compression.

Early applications of the free piston engine design were largely limitedto the use in air compressors and gasifiers. This limitation of use waslargely due to control issues. Once running, the fuel/air mixture wouldbe adjusted to the mechanical load for continuous operation. Anyvariation of mechanical loading would interfere with the powerequilibrium, thus requiring a readjustment in the fuel/air volume. Theadaptation to more general applications, such as a vehicle propulsionunit, proved to be problematic due to the control problems induced bythe constantly changing mechanical loading. A further limitation of asingle piston free piston design is that of vibration and noise as wasdiscovered in 1956 by General Motor's testing of the XP-500 prototypevehicle. In recent years, companies have begun to develop a Free-PistonEngine Linear Electrical Generator (FPEG) for use in hybrid vehiclesutilizing an opposed piston configuration which have addressed to someextent the vibration issues.

Conventional linear piston designs suffer from several limitations. Whenoperating as a free piston engine, some form of spring action must occurat each end of the piston travel. Failure to return the piston willresult in serious damage. Free piston designs are inherently a 2 strokedesign. While simpler than a 4 stroke solution, the 2 stroke (cycle) isless efficient with respect to fuel consumption and producesunacceptable exhaust emissions. Typically a 2 stroke design alsorequires lubrication to be mixed with the fuel. Conventional free pistonengines are difficult to control power settings due to the complexitiesof controlling piston oscillation.

Thus, there is a need for a free piston engine design that addresses thecontrol, vibration, and efficiency issues.

SUMMARY OF THE INVENTION

According to various embodiments, a linear piston electrical generatoris disclosed. The linear piston electrical generator includes aninternal combustion assembly comprising a piston housed within acylindrical combustion chamber, a linear power generator comprising amagnet assembly surrounded by a coil assembly, a pushrod connected tothe internal combustion assembly and the linear power generator, alimiter rod connected to the pushrod to control end limits for aposition of the piston, and a rotation disk connected to the limiterrod.

According to various embodiments, a piston linear electrical generatoris disclosed. The piston linear electrical generator includes a firstinternal combustion assembly and a first linear power generator; asecond internal combustion assembly and a second linear power generator;and a stroke limiter connected to the first internal combustionassembly, first linear power generator, second internal combustionassembly, and second linear power generator. The stroke limiter includesa first pushrod connected between the first internal combustion assemblyand the first linear power generator, a second pushrod connected betweenthe second internal combustion assembly and the second linear powergenerator, a first limiter rod connected to the first pushrod, a secondlimiter rod connected to the second pushrod, a first rotation diskconnected to the first limiter rod, and a second rotation disk connectedto the second limiter rod. The movement of the first pushrod associatedwith the first internal combustion assembly and the first linear powergenerator and the movement of the second pushrod associated with thesecond internal combustion assembly and the second linear powergenerator are oppositely phased.

According to various embodiments, a linear piston electrical generatorarrangement is disclosed. The arrangement includes a plurality of2-piston linear electrical generators coupleable in series, a buck/boostconverter coupled to one of the 2-piston linear electrical generators, aDC link coupled to the buck/boost converter, and a controller todetermine the operational state for each 2-piston linear electricalgenerator.

According to various embodiments, a hybrid electric vehicle isdisclosed. The hybrid electric vehicle includes an energy storagedevice, a traction drive coupled to the energy storage device, thetraction drive comprising a traction motor, and a plurality of 2-pistonlinear electrical generators coupled to the energy storage device.

According to various embodiments, a piston linear electrical generatoris disclosed. The piston linear electrical generator includes a firstinternal combustion assembly and a first linear power generator, asecond internal combustion assembly and a second linear power generator,and a stroke limiter connected to the first internal combustionassembly, first linear power generator, second internal combustionassembly, and second linear power generator. The stroke limiter includesa first pushrod connected between the first internal combustion assemblyand the first linear power generator, and a second pushrod connectedbetween the second internal combustion assembly and the second linearpower generator. The movement of the first pushrod associated with thefirst internal combustion assembly and the first linear power generatorand the movement of the second pushrod associated with the secondinternal combustion assembly and the second linear power generator areoppositely phased.

Various other features and advantages will be made apparent from thefollowing detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order for the advantages of the invention to be readily understood, amore particular description of the invention briefly described abovewill be rendered by reference to specific embodiments that areillustrated in the appended drawings. Understanding that these drawingsdepict only exemplary embodiments of the invention and are not,therefore, to be considered to be limiting its scope, the invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a single piston stroke limiter for alinear electrical power generator according to an embodiment of thepresent invention;

FIG. 2A is a graph illustrating a linear piston electrical generator(LPEG) piston position versus resolver angle according to an embodimentof the present invention;

FIG. 2B is a graph illustrating a LPEG piston position versus resolverangle according to another embodiment of the present invention;

FIG. 3A is a table illustrating the operation of the single pistonstroke limiter when operating as a 4-cycle internal combustion engineaccording to an embodiment of the present invention;

FIG. 3B is a table illustrating operation of a 2-piston linear electricgenerator when operating as a 4-cycle internal combustion engineaccording to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a 2-piston linear electric generatorwith stroke limiters and a permanent magnet synchronous motor (PMSM)according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a 2-piston LPEG combined cylinder andlinear power generator according to an embodiment of the presentinvention;

FIG. 6 is a schematic diagram of a 2-piston LPEG combined cylinder andlinear power generator according to an alternative embodiment of thepresent invention;

FIG. 7 is a schematic diagram of a 2-piston LPEG combined cylinder andlinear power generator according to another alternative embodiment ofthe present invention;

FIG. 8 is a schematic diagram of a 2-piston LPEG stroke limiteraccording to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a 2-cylinder energy collector moduleaccording to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a quad LPEG unit with a power combineraccording to an embodiment of the present invention;

FIG. 11 is a schematic diagram of a quad LPEG unit lubrication systemaccording to an embodiment of the present invention; and

FIG. 12 is a schematic diagram of a hybrid vehicle incorporating a quadLPEG unit according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The disclosed invention is an apparatus intended to be a key element ofa hybrid electrical power system. The hybrid power system may beutilized as a stationary (non-moving) application or a hybrid vehicle.The hybrid system will include 1 or more power modules consisting of aunified power generation system and incorporating an internal combustionassembly for each power module. The unified power system includes asupervising processor for managing each individual power module. Thepower modules may be selected to turn on or off. When turned on themodule will be commanded to produce a specified power amount by thesupervising processor.

FIG. 1 represents, with a cross sectional view, a single linked pistonelectrical generator including a linear power generator (1) according toan embodiment of the present invention. The linear power generator (1)includes a permanent magnet assembly (1A) that will mechanicallyoscillate back and forth in a linear motion located in a cylindersurrounded by a pickup coil (1B).

The motion of the magnet (1A) induces a bipolar voltage (V_(A), V_(B))in the coil (1B). The magnet (1A) is connected to an internal combustionassembly (6) by way of a pushrod (3). The pushrod (3) is attached to themagnet (1A) in the linear power generator (1) and a piston (6A) in theinternal combustion assembly (6). Both the magnet (1A) and piston (6A)move in an oscillatory manner in unison. The pushrod (3) is supportedand guided by multiple linearly arranged bearings (7). There is a smallgap (1C) between the magnet (1A) and a cylinder wall of the linear powergenerator (1). The gap (1C) insures that no frictional losses occurwithin the linear power generator (1).

The magnet (1A) is encapsulated by a linear coil assembly (1B) with ahollow center, permitting the magnet (1A) to move within the coilassembly (1B). The surface of the magnet (1A) comes close but does nottouch the inner walls of the linear coil (1B). The smaller the gapbetween the magnet (1A) and the inner wall of the linear coil (1B), thebetter the flux coupling will be between the magnetic field of themagnet (1A) and the linear coil (1B). As the magnet (1A) moves back andforth it will induce an electromotive force (EMF) in the linear coil(1B). The magnitude of the EMF voltage is proportional to the rate atwhich the magnet (1A) moves. The voltage produced by the linear coil(1B) will appear between terminals V_(A) and V_(B). The waveformproduced at terminals V_(A) and V_(B) will be sinusoidal in nature witha frequency dependent on the oscillation rate of the piston (6A) movingin the cylinder.

The internal combustion assembly (6) is shown in a simplified form forpurposes of clarity. Not shown are the lubrication system, air/fuelintake, exhaust ports (or alternatively valves), and ignition system.These are well known elements of an internal combustion type engine.Piston rings (not shown) surround the piston, are in direct contact withthe piston cylinder wall, and provide a seal for a combustion chamber(6B).

The combustion engine cylinder may be coated with a friction materialsuch as a tungsten-molybdenum disulfide polymer matrix coating or a hightemperature Teflon. A low viscosity lubrication oil such as 10w-30 maybe used to reduce piston friction, and therefore reduce energy loss aswell as reducing mechanical wear on the engine parts. The design of thecombustion engine assembly will depend on the cycle type (i.e. 2 or 4cycle, Otto, or diesel) and will dictate the friction reduction methodsemployed.

Key to operation of the internal combustion unit (6) is a limiter rod(4) and a rotation disk (5). The limiter rod (4) is mechanically coupledto the pushrod (3) via a crankpin (2). The limiter rod (4) is alsomechanically coupled to the rotation disk (5) via a crankpin (2). Thelimiter rod (4) controls the end limits for the position of the internalcombustion piston (6A). The limiter rod (4) operating in concert withthe pushrod (3) and the disk (5) define both top-dead-center (TDC) andbottom-dead-center (BDC) limits on the combustion piston (6A). The useof the limiter rod (4) and disk (5) is a feature that distinguishes thelinked piston design from conventional linear piston designs.

The crank pin (2) mounted on the rotation disk (5) defines the overallstroke limit of the internal combustion piston (6A). The distance fromthe center of the disk (5) to the center of the crank pin (2) is definedas R (Radius). The piston maximum stroke length is 2*R and equal to thelinear distance from TDC to BDC.

The disk (5) is connected by a gear pair with a 1:1 ratio. The firstgear is attached to the disk (5). The second gear is attached to arotary position resolver or rotary encoder (9A). The two gears mesh toform the 1:1 turning ratio. The resolver (9A) will produce a digitallyencoded signal indicating the shaft angle of the resolver.

The disk (5) serves another important purpose: the internal combustionassembly (6) produces energy (and therefore power) as a series ofcontrolled explosions or energy impulses. The disk (5) provides a“smoothing function” or integration function to absorb and release theenergy impulses produced by the ignition process and acts as a flywheel.

To thus overcome the limitations of conventional linear pistons, amechanism to limit the piston stroke excursion is introduced. The piston(6A) and magnet (1A) are connected by a pushrod (3) resulting in alinear bidirectional motion. The end limit of travel is determined bythe limiter rod (4) and rotation disk (5).

As indicated above, the piston (6A) and piston cylinder (6) are elementsof an internal combustion engine (ICE). A piston head (14) contains avalve assembly, including an intake valve and exhaust valve, and a sparkigniter. An ICE controller sequences the intake and exhaust valve motionin concert with the spark igniter to induce a reciprocating motion ofthe piston. These elements will be discussed in more detail below, withreference to FIG. 5 . The ICE controller adjusts the timing and sequenceof the head valves and ignitor using positional information from therotary encoder (9A). It should be noted that a linear position encoderconnected to the pushrod (3) can be used as an alternative to the rotaryencoder (9A).

Connected to the head (14) is a carburetor subassembly to mix fuel andair to produce a combustion mixture to be drawn into the piston cylinder(6B) for a controlled burn to extract the potential chemical energycontained in the fuel mixture. Carburation is best performed by a fuelinjector, to be shown in more detail in FIG. 5 , but may alternativelybe performed with a carburetor using a venturi effect drawing air induring an intake stroke of the piston (6A).

FIG. 2A is a graph of the stroke length as a function of encoderrotation angle. The stroke length of the piston and magnet assembly (1A)in the linear power generator (1) determines the oscillation frequencyof the magnet/piston pair. The power generated per stroke is determinedby the geometry of the piston cylinder and the linear coil (1B) in thepower generator (1). Stroke length limits are determined by the diameterof the disk (5) and the length of the limiter rod (4). As can be seen inFIG. 2 , stroke position as a function of resolve angle is a repeatingsinusoid. With the piston (6A) at TDC, the angle of the resolver shaftwill be 0 degrees. When the resolver (9A) output is indicating 180degrees, the piston (6A) will be at BDC.

A key limitation for conventional designs is the restriction of a2-stroke cycle of the internal combustion process. A 2-stroke cycle hasan inherent problem with the production of air pollution in its exhaustand is less efficient than the more complicated 4-stroke cycle. Theintroduction of the stoke limiter, which includes the pushrod (3), thelimiter rod (4), and the disk (5), permits the introduction of anefficient 4-cycle internal combustion design.

FIG. 3A is a table identifying the 4-cycle sequence for the mechanicalelements of FIG. 1 . Cycle A consists of the piston (6A) starting atTDC, with the intake valve open. The piston (6A) will move away from thecylinder head (14) drawing in a fuel mixture via the intake valve. Thisis the intake cycle. Once the piston (6A) reaches BDC the intake valvecloses and the piston reverses direction to start the compression cycle.With both intake and exhaust valves closed, and with the piston (6A)moving to TDC the compression cycle occurs.

During cycle A, in FIG. 3A, a motor/generator provides torque to therotation disk (5) (the motor/generator acts as an “active” flywheel)which in turn transfers a force to the pushrod (3) by way of the limiterrod (4) to induce linear motion to the piston/magnet pair. Themotor/generator motoring action in cycle A provides force to move thepiston (6A) down during the intake cycle and the compression cycle.

Once the piston (6A) reaches TDC during the compression cycle, cycle Bcommences with the power cycle, where an ignition spark ignites the fuelmixture. The controlled explosion forces the piston (6A) to BDC andcompletes the power cycle. Once reaching BDC the exhaust valve opens andthe piston (6A) reverses direction towards TDC to push the exhaust fumesout of the cylinder exhaust gas (exhaust cycle) completing cycle B.

During cycle B the motor/generator unit will absorb power on the powercycle and provide power to complete the exhaust stroke. It can be seenfrom FIG. 3A that the power transfer to the linear generator only occurson the power cycle.

The 4-cycle sequence may also be described as follows. Cycle 1 draws theair/fuel mixture into the piston cylinder (6) when the piston (6A) is attop dead center (TDC) (closest) to the cylinder head (14). The pistonwill move away from the cylinder head (14) creating a partial vacuum anddrawing in the fuel/air mixture into the cylinder (6). When the piston(6A) reaches bottom dead center (BDC) the first cycle will be complete.It should be noted that both TDC and BDC are specified by the limiterrod (3) and the disk (5)/rotary encoder (9A) assembly. Cycle 2 includesclosing the intake valve in the cylinder head (14) and the piston (6A)moving from bottom dead center to top dead center compressing thefuel/air mixture. Cycle 2 may be referred to as the compression cycle.Cycle 3 starts when the piston (6A) reaches TDC during cycle 2. Theigniter ignites the fuel/air mixture to create a controlled burn (orexplosion) forcing the piston (6A) away from the cylinder head (14). Theenergy released by the controlled burn is coupled to the magnet (1A) byway of the pushrod (3). Cycle 4 starts when the piston (6A) reaches BDCduring cycle 3. The piston (6A) will move toward the piston head (14)with the exhaust valve open, expelling the hot exhaust from the cylinder(6).

A limitation of the invention in FIG. 1 is that some mechanism must keeptrack of cycle A and cycle B to complete the full 4 cycle's sequence.Software, for example, could keep track of the cycle A completion andleading to cycle B start. A further limitation to the invention in FIG.1 is that the mechanical motion of the piston magnet pair is unbalanced,producing a vibration from the simple harmonic motion of thepiston/magnet pair.

FIG. 3A also shows the 4-stroke sequence from the perspective of therotary encoder (9A). The rotary encoder (9A) is coupled to the disk (5)using a gear or belt mechanism. The gearing ratio is 2 to 1 whereby therotary encoder (9A) turns at half the rate of the disk (5). By reducingthe angular rate of the rotary encoder (9A) with respect to the disk(5), the 4 cycle sequence of the ICE can be represented in a singlerotation of the rotary encoder (9A).

The challenge in making a 4-cycle ICE operate is that the intake,compression, and exhaust cycles require energy to keep the piston (6A)(pushrod (3)) in motion. With sufficient mass, the disk (5) can bothstore and release mechanical energy. Such a disk (5) is commonlyreferred to as a flywheel. The amount of mass in the flywheel willdetermine the amount of energy that can be stored in the flywheel as afunction of RPM.

The inertial mass of the flywheel will also determine how quickly arotation rate change of the flywheel can occur. The more mass there is,the slower a rate change can occur. Conversely, the higher the mass, thesmoother the operation of the ICE will be. The flywheel may beconsidered a low pass filter whereby the power impulses of the ICE areintegrated to provide a smoother operation of the ICE. The flywheel isconsidered to be a passive energy storage device.

As previously noted, the linear power generator (1) is connected to theICE piston (6A) by way of the pushrod (3). As the piston (6A) moves backand forth in the ICE cylinder (6), the magnet (1A) moves in concert withit. The magnet (1A) is preferably made of a neodymium formulationproducing a high gauss magnetic field. Other formulations may be usedsuch as nickel-cobalt but will produce a lower magnetic flux density.

FIG. 4 is a schematic diagram for an enhanced embodiment of theinvention that was illustrated in FIG. 1 . FIG. 4 shows a “Dual PowerModule” with 2 ICEs (6) and 2 power generators (1) mechanically coupledto a stroke limiter (10) including 2 disks (5), a permanent magnetsynchronous motor (PMSM) (8), and a resolver (9). The ICE/powergenerators (6)/(1) are phased so that they move in opposite directionswhen operated. The opposing motion results in force cancelation,minimizing operational vibration. The stroke limiter (10) provides for 3functions. It insures that the ICE/power generators (6)/(1) move inopposite directions, provides accurate position information from theresolver (9), and acts as an active flywheel. The active flywheelfunction uses the PMSM (8) to absorb energy when either piston isperforming a power stroke and provides energy on a compression, exhaust,or intake stroke. A key difference between the stroke limiter device inFIG. 1 when compared to the stroke limiter (10) in FIG. 4 is the 2:1gear ratio. The 2:1 gear ratio permits all 4 cycles of both pistons tobe tracked with a single rotation of the resolver shaft.

FIG. 3B is a table showing the operation of the invention found in FIG.4 . As shown by FIGS. 3A and 3B, the 4 cycles are the same with thedifference found in FIG. 3B where all 4 cycles occur in a singlerotation of the rotary encoder. This is due to the 2:1 gear between thelimiter disk (5) and the rotary encoder (9A).

FIG. 2B shows the relationship of both piston/magnet pairs found in FIG.4 . At 0 degrees both pistons will be at TDC on cycle A. At 90 degreesthe pistons will be at BDC of cycle A. At 180 degrees the pistons willbe at TDC cycle B. At 270 degrees the pistons will be at BDC on cycle B.Finally, at 0 degrees the 4 cycle sequence will start over.

FIG. 5 is a schematic diagram providing further detail with respect tothe embodiment found in FIG. 4 . Fuel control modules (13) control thefuel injector (6E) using pulse width modulation to mix fuel with theintake air (6D). Ignition control modules (12) provide high voltageenergy to the spark plug (6F). Valve control modules (11) electricallyactivate the intake valve (6G) and exhaust valve (6C). The fuel controlmodules (13), ignition control modules (12), and valve control modules(11) obtain sequencing signals from a power controller (17). The powercontroller (17) monitors position information from the piston resolver(9). An inverter/converter assembly (15) provides power control to thePMSM (8), which is a 3 phase brushless motor and acts as an activeflywheel. Capacitor C1 provides and receives electrical energy dependingon the mode of operation of the 3 phase PMSM (8). When the motor (8) isin regeneration (absorbing energy), capacitor C1 is charged. When themotor (8) is producing mechanical power, capacitor C1 discharges.Capacitor C1 is also supplied with supplemental energy from a DC busexternal to the linear electrical power generator. Diode DO is anisolation diode that keeps energy from coming back to the power supply.The supplemental energy is used for ICE starting and provides additionalenergy during the intake, compression, and exhaust cycles of the ICEunits. The energy collector (16), to be further detailed in FIG. 9 ,collects electrical energy from the 2 linear power generators (1) andprovides the collected energy to an power combiner external to thelinear electrical power generator.

FIG. 6 illustrates an enhancement to the embodiment shown in FIG. 5 .The linear power generators (1) have been relocated such that they arecoupled to the piston cylinder assemblies (6) as opposed to the opposingside of the stroke limiter (10). This configuration provides for a morecompact mechanical design.

FIG. 7 illustrates a further compaction of the invention found in FIG. 6. As shown in FIG. 7 , both ICE/linear power generator pairs (6)/(1) arelocated on the same physical side of the stroke limiter (10).

FIG. 8 provides further details of the mechanical elements found withinthe stroke limiter (10) as shown in FIG. 7 . It should be noted that theICE/power generators (6)/(1) are phased in opposing directionsconsistent with the previous embodiments as found in FIGS. 4-7 .

FIG. 9 is a schematic diagram for the electrical energy collector module(16).

Within each 2-piston power generator are 2 linear coil electrical powergenerators. Each linear coil produces electrical voltage that isbipolar. Energy is primarily collected during the power stroke of eachcylinder.

In an off line state the Enable Contactor SC2 is open and the BypassContactor SC4 is closed. The contactors discussed herein may be anysolid state switching devices, but mechanical switching devices arepreferred for safety reasons.

To sequence the 2 cylinder energy collector on line the followingsequence occurs:

The 2 cylinder energy collector module (16) collects energy from the twolinear generators (1). As the energy from each linear generator (1) hasboth a positive and negative voltage component, diodes D8 and D10 coupleelectrical energy into the collector module only passing the positivecomponent from each generator (1). To boost the voltage the Q1 and Q2IGBTs are turned on and off during the proper portion of the energygeneration stroke to inductively boost the generated voltage. Q1 and Q2may be any kind of semi-conductor switching device, but IGBTs arepreferred. The inductive element includes the linear generator coils(1B), as shown in FIGS. 1 and 4 . A 50% duty cycle on the IGBT gateinput will provide for a voltage boost of 2:1.

The combination of Q1 and diode D9, and the combination of Q2 and diodeD11 creates two individual inductive boost circuits when combined withits respective linear generator coil. This boosted voltage chargescapacitor C2 through a pre-charge resistor R1 to bring up the voltage onC2 without causing excessive currents. Once the voltage (V_(PRE)) at thecapacitor C2 indicates the capacitor C2 is charged, a Pre-ChargeContactor SC1 is closed, bypassing the pre-charge resister R1 so fullpower can be used from the boost circuit.

The power controller (17) controls the pulse width modulation suppliedto IGBTs Q1 and Q2 to create the required level of boost to maintain thevoltage (V_(PRE)) at the desired voltage. The Pre-Charge Contactor SC1is controlled by the power controller (17) based on reading the voltage(V_(PRE)) to bypass the pre-charge resistor R1.

To enable the 2 cylinder energy collector (16) into service, the EnableContactor SC2 is closed and the Bypass Contactor SC4 is open.

To remove the 2 cylinder energy collector (16) from operation, it mustbe sequenced to a quiescent state under control of the power controller(17). Boosting functions are discontinued and the Pre-Charge ContactorSC1 is open. A Discharge Contactor SC3 is closed to bleed off capacitorC2 through a discharge resistor R2. The Enable Contactor SC2 is open andthe Bypass Contactor SC4 is closed to bypass the 2 cylinder energycollector (16).

FIG. 10 is a schematic diagram of a power combiner (20) embodiment withfour identical power modules (22) in a “Quad Unit” LPEG arrangement thatare independently controlled and respective powers are selectivelycombined. While four power modules are used in this embodiment, itshould be understood that other pluralities may be used. Each powermodule (22) is of the configuration as found in FIG. 7 . The powercombiner (20) also incorporates the lubrication system found in FIG. 11, to be discussed in more detail below. The master control (21)determines the operational state for each power module (22). By example,if each power module (22) is capable of producing 10 kW, the overallpower generation is 0 to 40 kW (minus losses). The function of theindividual energy collector modules (16) within the power modules (22)permits the power modules (22) to be electrically connected in series.The additive voltage aspect produces a large dynamic range of voltageand power. It is preferable to electrically connect the power modules(22) in series, but it is also possible to connect them in parallel. Thebypass contactor SC4 in each energy module (16) permits 16 possiblecombinations of the 4 power modules (22). A software scheduling methodmay keep track of individual power module activity and allow for anearly equal distribution of use, thereby simplifying maintenancescheduling. It is also possible to take one or more power modules (22)“offline” due to a fault and allow the remaining modules (22) to meetthe power demands.

The regulated unidirectional buck-boost converter (24) adapts the powerand voltage of the power module stack to the target demands of thevariable DC link. The DC link may be used to charge an external highvoltage battery, provide power to a motor inverter, or to a fixedfrequency DC to AC inverter. The buck-boost converter (24) alsocompensates and minimizes the DC ripple inherently produced by the powermodules (22).

FIG. 11 is a schematic diagram showing details of a Quad Unit LPEGlubrication system. The dual power module mechanics require lubricationto all the moving parts. As each power module (25) operatesindependently, its oil circulation is designed to functionindependently. The independent operation has several advantages over aunified oil circulation system. Each power module (25) can be active orinactive without affecting the other power modules (25). The failure ofa power module (25) will not interfere with the operation of theremaining power modules (25). Oil pressure (27) is available for eachpower module (25), allowing for decisions to determine if the unit isfit for operation. A common oil reservoir (33) contains the oil for thefour power modules (25). The oil pump (28) draws oil from the reservoir(33). The oil pump (28) is activated by the lubrication controller (23).Oil is pumped through an oil filter (26) to feed the piston assemblies(6). The oil continues its path through the piston assemblies (6) and isreturned to the oil reservoir (33). An oil pressure sensor (27) islocated between the output of the oil pump (28) and the input of the oilfilter (26) and is monitored by the lubrication controller (23). Thelubrication controller (23) makes decisions based on commands from themaster controller (35) and the oil pressure sensors (27) to control theoil pumps (28) in the power modules (25).

The oil reservoir (33) is monitored for oil level, oil temperature, andoil pressure. An oil level low indication is passed from the lubricationcontroller (23) to the master controller (35) should the oil level fallbelow operating parameters. Another pressure sensor (34) is read by thelubrication controller (23) to determine if the oil reservoir requirespressure equalization by opening a pressure relief valve. Thetemperature of the contents of the oil reservoir (33) is controlled bythe lubrication controller (23). Based on predetermined temperaturethresholds, a cooling pump (29) is activated by the lubricationcontroller (23) pumping the oil through an oil filter (30), then througha radiator (32), and back into the oil reservoir (33). Additionally, thelubrication controller (23) operates a fan (31) to force airflow throughthe radiator (32) to assist in cooling. A pressure sensor (27A) ismonitored to assess the condition of the oil cooling path.

FIG. 12 is a schematic diagram of a hybrid vehicle incorporating a quadpower module unit with power converter as shown in FIG. 10 , whichcreates a scalable system for generating power to charge a high voltage(HV) battery and run the traction motor.

As a plug-in hybrid, an AC plug charger (36) is connected an HV battery(41) through a relay (37). A battery management system (40) controls thecharging of the HV battery (41) in conjunction with a master systemcontroller (44) and the charger (36).

In the hybrid mode, the relay (37) connects the HV battery (41) to abuck/boost converter (38). Based on a call for torque, the master systemcontroller (44) instructs the buck/boost converter (38) in conjunctionwith a traction inverter/converter assembly (39) to run the tractionmotor/generator (42) at the requested speed. The speed and direction isdetermined by reading a resolver (43). During braking, the tractionmotor/generator (42) generates power to charge the HV battery (41)through the traction inverter/converter assembly (39) and the buck/boostconverter (38).

As the demand for power goes up or the state of charge of the HV battery(41) goes down a quad power module unit with power combiner (20) iscalled by the master system controller (44) to supply additional power.The power generated can be used to charge the HV battery (41), run thetraction motor/generator (42), or both. As the quad power module unitwith power combiner (20) is made up of four complete LPEG generators, asshown in FIG. 10 , the amount of power generated can be controlled bythe number of units called into service. Based on the need, anycombination of the four LPEG Generator units can be called into service.

As such, disclosed herein is a load adaptive linear electrical generatorsystem for generating DC electrical power. The DC power may betransformed to AC with a single or multiple phase electrical inverter.The electrical generation system includes 1 or more power generationmodules which will selectively turn on or off and additivity contributepower depending on the DC power demand. Each power generating moduleincludes one or more pairs of a linear electrical generators connectedto an internal combustion piston based power assembly. The piston in theinternal combustion assembly is connected to a magnet in the linearelectrical generator. The piston/magnet assembly oscillates in a simpleharmonic motion; at the frequency dependent on power load of theelectrical generator. A stroke limiter constrains the piston/magnetassembly motion to preset limits. A control element senses a powerdemand (request) and will determine how many power modules are requiredto meet or exceed the power demand. On time accumulation for each powermodule is recorded and a rotation schedule is established whereby eachpower module provides the same approximant energy over the overallelapsed time of operation for the power generator.

It is understood that the above-described embodiments are onlyillustrative of the application of the principles of the presentinvention. The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope. Thus, while the presentinvention has been fully described above with particularity and detailin connection with what is presently deemed to be the most practical andpreferred embodiment of the invention, it will be apparent to those ofordinary skill in the art that numerous modifications may be madewithout departing from the principles and concepts of the invention asset forth in the claims.

What is claimed is:
 1. An apparatus comprising: a plurality of powermodules for producing respective voltages at respective outputs whenactivated, the plurality of power modules being configured to beselectively activated and deactivated; a combiner coupled to the outputsof the power modules, the combiner configured to selectively produce avoltage produced by a single activated power module or a combination ofvoltages produced by a plurality of activated power modules; theplurality of power modules are coupled in series to produce a sum of thevoltages produced at the outputs of activated respective power modules;and a controller configured to: selectively activate and deactivate oneor more of the plurality of power modules coupled in series; and controlthe activation and deactivation to produce about an equal distributionof use of the plurality of power modules coupled in series.
 2. Theapparatus of claim 1, wherein the controller is further configured todeactivate at least one of the plurality of power modules based on afault.
 3. The apparatus of claim 1, wherein each power module comprisesan internal combustion engine receiving lubrication from a common oilreservoir of a lubrication system.
 4. The apparatus of claim 1, whereinthe combiner is configured to be coupled to a high voltage battery of anelectric vehicle.
 5. The apparatus of claim 1 wherein the combiner isconfigured to be coupled to a motor of an electric vehicle.
 6. Theapparatus of claim 1, wherein the combiner is configured to be coupledto a motor inverter of an electric vehicle.
 7. The apparatus of claim 1,wherein the combiner is configured to be coupled to a buck/boostconverter.
 8. The apparatus of claim 1, wherein each power modulecomprises: a first and a second electrical generator, each electricalgenerator comprising an internal combustion assembly and a powergenerator, each power generator comprising an inductive element forproducing a respective voltage, each of the electrical generatorscomprising a respective pushrod coupled between a respective internalcombustion assembly and a respective power generator, each of theinductive elements comprising a magnet coupled to the respective pushrodand a coil surrounding the magnet, the internal combustion assembliesconfigured to move the respective pushrods in opposite directions, thefirst and second electrical generators configured to produce respectivevoltages at different phases corresponding to different power stokes ofthe respective internal combustion assemblies; a capacitor; and aswitching circuit coupled between the respective inductive elements ofthe first and second electrical generators and the capacitor forselectively coupling the same portion of the voltages produced by therespective inductive elements of the first and second electricalgenerators to the capacitor to develop an output voltage.
 9. Theapparatus of claim 8, wherein each power module further comprises afirst and a second boost circuit, each boost circuit comprising therespective inductive element of the first and second power generatorsfor boosting the respective voltages produced by the respectiveinductive element.
 10. The apparatus of claim 9, wherein operations ofthe boost circuits are synchronized to power strokes of respectiveinternal combustion assemblies.
 11. The apparatus of claim 8, whereineach switching circuit comprises first and second switching devices eachcoupled to the respective inductive element of the first and secondelectric generators.
 12. The apparatus of claim 8, wherein each powermodule further comprises a pre-charge circuit coupled between theswitching circuit and the capacitor, the pre-charge circuit beingconfigured to be selectively activated to pre-charge the capacitor. 13.The apparatus of claim 8, wherein each power module further comprises adischarge circuit coupled to the capacitor, the discharge circuit beingconfigured to be selectively activated to discharge the capacitor whenthe first and second electrical generators are not activated.
 14. Theapparatus of claim 1, wherein the controller is further configured toselectively activate the plurality of power modules based on a powerdemand of a load.